The present invention relates to storm water flow restrictors, and in particular to an external flow restrictor that is easily installed, and has a varying flow rate.
Many buildings have substantially flat roofs which collect storm water during a rainfall. The storm water collected on the roof is typically quickly drained off of the roof through a roof drain. The term “flat roofs” is not limited to a roof that is flat. Even roofs referred to by those skilled in art as a “flat roof’ typically have a pitch or low point to direct water collected on the roof to a specific location on the roof or towards a roof edge. The drain generally extends through an opening formed in the roof material at a low point in the roof. The opening must be sealed around the drain to prevent water from leaking through the opening into the building.
The drain is often connected to a storm sewer, or combined sanitary and storm sewer, system provided by a local municipality that can channel the storm water from the roof to a treatment facility or point of discharge. The treatment facility treats the combined storm water and sewage (sewage/water) for safe discharge into the environment, or for use by local citizens. If the sewage/water collected in the sewage system exceeds the treatment capacity of the treatment facility, the sewage/water in the system must be stored until the treatment facility can treat it, or be released untreated into the environment. Unfortunately, releasing untreated sewage/water can cause health problems for the local citizens, and may result in fines from local, state, and federal environmental agencies.
A variety of methods can be employed by the municipalities to avoid releasing untreated sewage/water into the environment. As discussed above, the sewage/water can be stored until the treatment facility can treat it. In one municipality, sewage/water storage facilities, such as tunnels bored in bedrock beneath the municipality's surface was created. However, this method is expensive, and not always an efficient use of taxpayer's dollars in view of the expected heavy rainfalls for a particular climate.
Another method includes increasing the capacity of the treatment facility to handle larger volumes of sewage/water. However, as in building storage facilities for excess sewage/water, building larger facilities is expensive, and the rainfalls which require the larger capacity treatment facilities is an infrequent event which would result in the extra capacity being unused most of the time.
Another method includes shutting off or restricting the flow of storm water into the sewer system. Shutting off the flow of storm water and, arbitrarily restricting the flow of storm water, into the system can result in flooding which is destructive to citizens property and dangerous to the citizens. Restricting the flow of storm water at specific entry points into the system, however, can be an inexpensive and effective way to store storm water until capacity at the treatment facility can accommodate the stored stormed water combined with sewage.
One group of entry points that can be restricted, under specific conditions, without detriment, is roof drains on flat roofs. This method can be accomplished through legislation that requires building owners to restrict the flow of water into roof drains. The storm water collected on the roof can be slowly drained into the sewer system without causing surcharging of the sewer system or flooding on the ground. Collecting storm water on a roof, however, has limitations. Roofs are typically designed to have at least a minimum structural capacity to support an anticipated live roof load that consists of rain, snow, and the like. If the volume of storm water stored on the roof exceeds the structural capacity of the roof, the roof could collapse. Roof drains are typically designed to quickly drain water off of the roof. Fortunately, typical building codes require roofs to have sufficient structural capacity that can support a substantial volume of water in addition to a secondary drain that is independent of the roof drain.
Flow restrictors are available which restrict the flow of storm water into a drain, such as the flow restrictor disclosed in U.S. Pat. No. 3,357,561. This flow restrictor is fixed to a drain sump and is enclosed by a debris guard. The restrictor has a plurality of notches that define a free area that is smaller than the free area of the drain pipe to restrict the flow of water into the drain. As a result, the flow of water into the drain is less than the maximum flow capacity of the drain pipe it is connected to.
The flow restrictor disclosed in U.S. Pat. No. 3,357,561 forms part of the drain assembly that must be at least partially disassembled to change or remove the flow restrictor. Because this type of drain assembly is manufacturer specific, the flow control portion of one drain assembly is not compatible with a drain assembly provided by a different manufacturer. As a result, if a flow restrictor is required for an existing drain, the entire drain assembly must be replaced. Replacing the drain assembly requires disassembling the existing drain, and often requires replacing the sump with a new sump that can accommodate the flow restrictor. Replacing a sump requires breaking the seal between the sump and the roof material. This can often result in leaks if the seal to the new sump is not properly installed, and may void roof warranties. Moreover, disassembling the old drain can be time consuming and expensive. Accordingly, a need exists for a flow restrictor which universally fits all roof drains, and does not require disassembling or replacing an existing drain.